Primed for Gmail centric users, 1.0 takes the look and feel of the browser translating it to an app that closely resembles Twitter's Mac client (formerly known as Tweetie for Mac.) A joy to use, it's robust interface easily replaces what Apple's Mail client lacks. While still lacking IMAP support for other providers, Sparrow is readying version 1.1 converting it to a full-featured mail client that will be compatible with other IMAP services. Download it today and change the way you communicate!

For others wondering if a "lite" version will be released, as noted by @sparrowmailapp in response: